Natural rubber, which is a polymer (cis-1,4-polyisoprene, m.w.≥1,000 kDa) composed of 320-35,000 isoprene molecules, is one of the most important polymers obtained from plants and is used as a natural material for a variety of products including medical devices, tires, belts, etc. Natural rubber is synthesized by sequentially adding isopentenyl diphosphate to a priming molecule under catalysis by a class of enzymes, called prenyltransferases.
Natural rubber exhibits excellent practical features in elasticity, flexibility, resilience, and wear resistance which cannot be compared to those of synthetic rubber. As many as about 2,500 plants including guayule (Parthenium argentatum) and Ficus carica are reported to produce natural rubber, but the industrially available sole source of natural rubber is the rubber tree (Hevea brasiliensis), which produces natural rubber with high molecular weights. Most of the natural rubber used in practical life is known to be obtained from the rubber tree.
However, the rubber tree is of low genetic diversity associated with vulnerability to the attack of pest insects, and the danger that the latex fluid therefrom might act as an allergen to human bodies has been raised (Mooibroek h, Cornish k. Microbiol. Biotechnol. 53:355-365 (2000)). For such reasons, efforts have been attempted to biosynthesize natural rubber with the aid of genetic recombination technology in addition to searching for alternative plants producing natural rubber. For example, genes associated with the biosynthesis of natural rubber, such as prenyltransferase in the rubber tree, were isolated and reported (PCT WO/01/21650; Shimizu et al., J. Biol. Chem. 273:19476-19481 (1998); Apfel et al., J. Bacteriol. 181:483-492 (1999); Sato et al., Mol. Cell. Biol. 19:471-483 (1999); AUTHORS Kim, et al., J. Exp. Bot. 55 (396), 377-385 (2004)), and an attempt was made to biosynthesize natural rubber by use of genetic recombination technology in Arabidopsis thaliana (PCT/US2000/25856).
The present invention also discloses a method for producing natural rubber by use of a recombinant microorganism such as E. coli. 